The objective of the proposed research is a unified, quantitative theory of binaural interaction that is applicable to a wide variety of binaural phenomena and that is consistent with neurophysiological data on the auditory system. This research involves both psychophysical experimentation and theoretical modeling and will include further studies of both interaural sensitivity and subjective attributes of the binaural image space. The proposed activities will capitalize on our highly-developed laboratory facilities, on modeling techniques derived from statistical communications theory, and on the systematic physiological data now available describing the peripheral transduction from acoustic waveforms to auditory-nerve firing patterns. The research is primarily concerned with the development of a mathematical description of a central processor that operates on the firing patterns as inputs and leads to psychophysical performance equivalent to that exhibited by human listeners. Included among the specific problem areas addressed are lateralization of tones, sensitivity to interaural correlation for random noise, the influence of lateralization-adaptation and earphone-head acoustic coupling variability on binaural experiments, and binaural interaction in hearing-impaired listeners.